A steam turbine converts heat energy into mechanical energy for driving equipment such as generators, compressors, and pumps. The heat energy provided to the steam turbine is in the form of high temperature steam routed into the steam turbine. Steam turbines comprise a housing or shell, and at least one pressurized section, wherein each pressurized section comprises a plurality of stages having a plurality of rotating parts and a plurality of stationary parts.
Rotating components include a rotor and a plurality of buckets. The rotor extends through the pressurized section and is rotatably supported adjacent a shell member of the pressurized section. A portion of the rotor is operably couplable to a machine, to transfer energy thereto. The plurality of buckets is secured to the rotor and rotate with the rotor.
High temperature steam enters the pressurized section through at least one fluid inlet passageway. The steam is routed at a high velocity to a plurality of blades of a first stage. When the high velocity steam contacts the plurality of blades, the rotor begins to or continues to rotate. At each successive stage of the steam turbine, the same type of rotation is induced or continued. Steam having passed through the plurality of stages in the steam turbine exits the pressurized section and may be rerouted to another pressurized section of the steam turbine.
Although a majority of the steam performs work in the steam turbine by flowing through a plurality of stages as described above to rotate the rotor, there is a portion of the steam, leakage steam, that is lost to the work generation process. Leakage steam does not perform work in the steam turbine because the leakage steam does not rotate the rotor. Leakage steam that does not rotate the rotor in the steam turbine represents a loss of rotor torque.
Sealing members are used in the steam turbine to reduce the flow of leakage steam. Rotor torque of the steam turbine may be increased by reducing an amount of leakage steam. An example of a sealing member is an end packing head. One end packing head is generally positioned near end portions of a pressurized section of the steam turbine. For example, one end packing head is disposed over a portion of the rotor at an upstream side of a first stage plurality of buckets.
The end packing head is configured to reduce an amount of steam flowing between the end packing head and the rotor in a direction away from the first stage plurality of buckets. However, a measurable amount of leakage steam still undesirably passes between the rotor and the end packing head.
Accordingly, it is desirable to use steam that has previously performed work in the steam turbine to reduce an amount of steam that can flow between a sealing member and the rotor to make more steam available to rotate the rotor, thereby increasing rotor torque of the steam turbine.